What is a Compact Antenna Test Range (CATR)?

A Compact Antenna Test Range, often shortened to CATR, is a specialized type of anechoic chamber designed to create a plane-wave test environment in a compact space. In free space, a device under test should ideally be evaluated at distances where the spherical wavefront emitted by the antenna has flattened into a plane wave. However, reaching that distance in a traditional far-field setup requires very large chambers, which can be impractical for high-frequency testing. A CATR chamber solves this problem by using a large precision reflector that reshapes the spherical waves from a feed antenna into a uniform plane wave within a defined quiet zone. Inside this zone, the device under test experiences the same conditions as it would in the far field, but within a much smaller physical footprint. This approach reduces facility size, cost, and complexity while still allowing accurate characterization of antennas and wireless devices across a wide range of frequencies.

How do CATR chambers support 5G and 6G mmWave OTA testing?

Millimeter-wave (mmWave) frequencies used in fifth-generation (5G) and emerging sixth-generation (6G) systems bring new challenges for testing. Antennas become smaller, but their arrays are more complex, often using beamforming and beam steering techniques to achieve high data rates and directional coverage. Because these systems rely on accurate spatial performance, testing must be conducted over the air (OTA) in controlled environments. CATR chambers are particularly well-suited for this. The compact quiet zone they generate provides a stable and repeatable environment for evaluating mmWave devices without requiring the extremely long distances of direct far-field chambers. This makes it possible to measure radiation patterns, beam accuracy, and throughput under realistic propagation conditions while maintaining manageable chamber dimensions. For 6G research, where frequencies are expected to extend beyond 100 gigahertz, the precise plane-wave field created in a CATR becomes even more critical. Researchers can validate new antenna designs, phased arrays, and integrated transceiver modules in a way that mirrors the conditions they will encounter in deployment, but within the controlled and repeatable environment of the chamber.

What’s the difference between CATR, direct far-field, and near-field OTA test methods?

Over-the-air (OTA) testing can be conducted using different approaches, and the choice depends on the frequency range, device size, and accuracy requirements. In a direct far-field chamber, the device under test is placed at a distance where the emitted wavefront is already planar due to the natural spreading of the spherical wave. This method is straightforward and highly accurate, but the distances required can be very large, especially at lower frequencies where antennas are physically larger. Such chambers can reach tens of meters in length, making them impractical for mmWave testing. A near-field chamber measures the electromagnetic field near the device, capturing data at many points across a surface or volume. Mathematical transformations are then applied to convert these near-field measurements into far-field results. This approach allows testing in smaller spaces and is useful for large antennas or devices, but it can require more complex post-processing and longer measurement times. A CATR chamber offers a middle ground. By using a reflector to generate a plane wave in a compact quiet zone, it replicates far-field conditions without needing the physical length of a direct far-field setup. Unlike near-field methods, it does not rely heavily on mathematical reconstruction, which simplifies the measurement process. For mmWave and sub-terahertz testing, where wavelengths are short and chamber space is at a premium, the CATR approach provides an efficient and practical solution.

Compact Antenna Test Range

Fast, accurate OTA measurements across your workflow

Keysight’s Compact Antenna Test Ranges (CATR) deliver highly repeatable over-the-air measurements from sub-6 GHz to mmWave frequencies in compact, integrated enclosures. Designed for 5G, 6G, and satellite communication device testing, as well as antenna measurements and phased array calibration, these turnkey chambers combine precision reflector technology, wide angular coverage, and low-reflection environments to enable consistent, standards-compliant results without the footprint of a full anechoic chamber. Whether you're performing R&D, conformance, or production testing, Keysight CATR chambers support high dynamic range, fast switching, and automated test control to accelerate your device evaluation with confidence. For applications requiring larger test volumes, Keysight also offers custom solutions with quiet zones of up to 2.4 meters, enabling accurate testing of heavier and larger devices such as base stations, satellites, and radar systems. Please contact Keysight to discuss your specific requirements. Need help selecting? Check out the resources below.

Reduce test time

Accelerate measurements with high-speed switching, automation support, and efficient OTA workflows to reduce overall test time.

Spatial accuracy

Achieve precise far-field conditions using precision reflectors and absorbers that create uniform quiet zones with minimal reflections.

Frequency coverage

Validate devices across sub-6 GHz, FR1, and mmWave FR2 bands using wideband feeds and optimized chamber designs for reliable performance.

Measurement repeatability

Ensure consistent results with low-reflection environments and stable mechanical configurations that minimize test variability.

Maximum angles of arrival

1 to 2
Frequency range

24 GHz to 42 GHz, 24 GHz to 55 GHz, 17 GHz to 30 GHz, 24 GHz to 43.5 GHz, 60 GHz to 90 GHz
Measurement type

Indirect far field (IFF)
Maximum DUT weight

10 kg to 10 kg (UE)|40 kg (gNB)
Use cases

RF / demodulation / RRM 1AoA verification and acceptance, Antenna measurement, FR2 UE RF in-band only verification, FR2 UE RRM 1AoA verification, Radar manufacturing, Radar design and verification, NTN RF verification, FR2 gNodeB